Japanese encephalitis virus hijacks ER-associated degradation regulators for its replication.

Flaviviruses target their replication on membranous structures derived from the ER, where both viral and host proteins play crucial structural and functional roles. Here, we have characterized the involvement of the ER-associated degradation (ERAD) pathway core E3 ligase complex (SEL1L-HRD1) regulator proteins in the replication of Japanese encephalitis virus (JEV). Through high-resolution immunofluorescence imaging of JEV-infected HeLa cells, we observe that the virus replication complexes marked by NS1 strongly colocalize with the ERAD adapter SEL1L, lectin OS9, ER-membrane shuttle factor HERPUD1, E3 ubiquitin ligase HRD1 and rhomboid superfamily member DERLIN1. NS5 positive structures also show strong overlap with SEL1L. While these effectors show significant transcriptional upregulation, their protein levels remain largely stable in infected cells. siRNA mediated depletion of OS9, SEL1L, HERPUD1 and HRD1 significantly inhibit viral RNA replication and titres, with SEL1L depletion showing the maximum attenuation of replication. By performing protein translation arrest experiments, we show that SEL1L, and OS9 are stabilised upon JEV infection. Overall results from this study suggest that these ERAD effector proteins are crucial host-factors for JEV replication.

Japanese Encephalitis Virus-Infected Cells.

RNA virus infections have been a leading cause of pandemics. Aided by global warming and increased connectivity, their threat is likely to increase over time. The flaviviruses are one such RNA virus family, and its prototypes such as the Japanese encephalitis virus (JEV), Dengue virus, Zika virus, West Nile virus, etc., pose a significant health burden on several endemic countries. All viruses start off their life cycle with an infected cell, wherein a series of events are set in motion as the virus and host battle for autonomy. With their remarkable capacity to hijack cellular systems and, subvert/escape defence pathways, viruses are able to establish infection and disseminate in the body, causing disease. Using this strategy, JEV replicates and spreads through several cell types such as epithelial cells, fibroblasts, monocytes and macrophages, and ultimately breaches the blood-brain barrier to infect neurons and microglia. The neurotropic nature of JEV, its high burden on the paediatric population, and its lack of any specific antivirals/treatment strategies emphasise the need for biomedical research-driven solutions. Here, we highlight the latest research developments on Japanese encephalitis virus-infected cells and discuss how these can aid in the development of future therapies.

Guanylate-binding proteins in virus infection.

Guanylate-binding proteins (GBPs) are immune GTPases that are induced in response to interferon stimulation/pathogen infection. These proteins arose early in evolution and have multiple physiological roles ranging from tumor suppression to anti-microbial functions. While several studies describe their mechanistic role in the lysis of bacteria/pathogen vacuole, and activation of the inflammasome, their functions in viral infections are only just emerging. The role of the GBPs in virus infections is multifaceted, being both dependent on and independent of GTP binding/hydrolysis and isoprenylation. Diverse antiviral roles are documented such as inhibition of viral RNA/protein synthesis, block of viral envelope glycoprotein processing, and targeting viral protein for degradation. Not surprisingly, several viral proteins bind to specific GBPs and antagonize their antiviral effects. While recruitment of GBP1, Gbp1, Gbp2 on the virus replication complex has been reported, the functional implications of this are not entirely clear. Furthermore, their role in interferon and inflammation activation during virus infection are contradictory, with reports of both positive and negative regulation. Here, we discuss the emerging functional roles of GBPs in virus infections.

Proteomic landscape of Japanese encephalitis virus-infected fibroblasts.

Advances in proteomics have enabled a comprehensive understanding of host-pathogen interactions. Here we have characterized Japanese encephalitis virus (JEV) infection-driven changes in the mouse embryonic fibroblast (MEF) proteome. Through tandem mass tagging (TMT)-based mass spectrometry, we describe changes in 7.85 % of the identified proteome due to JEV infection. Pathway enrichment analysis showed that proteins involved in innate immune sensing, interferon responses and inflammation were the major upregulated group, along with the immunoproteasome and poly ADP-ribosylation proteins. Functional validation of several upregulated anti-viral innate immune proteins, including an active cGAS-STING axis, was performed. Through siRNA depletion, we describe a crucial role of the DNA sensor cGAS in restricting JEV replication. Further, many interferon-stimulated genes (ISGs) were observed to be induced in infected cells. We also observed activation of TLR2 and inhibition of TLR2 signalling using TLR1/2 inhibitor CU-CPT22-blocked production of inflammatory cytokines IL6 and TNF-α from virus-infected N9 microglial cells. The major proteins that were downregulated by infection were involved in cell adhesion (collagens), transport (solute carrier and ATP-binding cassette transporters), sterol and lipid biosynthesis. Several collagens were found to be transcriptionally downregulated in infected MEFs and mouse brain. Collectively, our data provide a bird's-eye view into how fibroblast protein composition is rewired following JEV infection.

Methotrimeprazine is a neuroprotective antiviral in JEV infection via adaptive ER stress and autophagy.

Japanese encephalitis virus (JEV) pathogenesis is driven by a combination of neuronal death and neuroinflammation. We tested 42 FDA-approved drugs that were shown to induce autophagy for antiviral effects. Four drugs were tested in the JE mouse model based on in vitro protective effects on neuronal cell death, inhibition of viral replication, and anti-inflammatory effects. The antipsychotic phenothiazines Methotrimeprazine (MTP) & Trifluoperazine showed a significant survival benefit with reduced virus titers in the brain, prevention of BBB breach, and inhibition of neuroinflammation. Both drugs were potent mTOR-independent autophagy flux inducers. MTP inhibited SERCA channel functioning, and induced an adaptive ER stress response in diverse cell types. Pharmacological rescue of ER stress blocked autophagy and antiviral effect. MTP did not alter translation of viral RNA, but exerted autophagy-dependent antiviral effect by inhibiting JEV replication complexes. Drug-induced autophagy resulted in reduced NLRP3 protein levels, and attenuation of inflammatory cytokine/chemokine release from infected microglial cells. Our study suggests that MTP exerts a combined antiviral and anti-inflammatory effect in JEV infection, and has therapeutic potential for JE treatment.

Concomitant multiple subretinal cysticerci in neurocysticercosis.

We present a unique case of asymptomatic NCC that was accidently diagnosed on radiological investigations after a road traffic accident. An Ophthalmologic consult was sought to rule out intraocular or optic nerve cysticercosis. Fundoscopy showed multiple white-pale yellow lesions in the right eye which on ultrasonography confirmed cyst lined by a cyst wall consistent with subretinal cysticercosis. The patient was treated with diode laser photocoagulation. A high index of suspicion is required to diagnose NCCin endemic areas. In the right eye which on ultrasonography confirmed cyst lined by a cyst wall consistent with subretinal cysticercosis. The patient was treated with diode laser photocoagulation.

Fulminant Orbital Cellulitis - A Rare Presentation of Endogenous Endophthalmitis.

BACKGROUND: Endogenous endophthalmitis refers to the intraocular infection resulting via haematogenous spread from the distant foci. Dengue is an important health problem in India with varied ophthalmic manifestations either due to viremia, immunologic phenomenon, or haemorrhagic tendency. CASE: We report an unusual presentation of endogenous endophthalmitis as fulminant orbital cellulitis in a young adult patient having a history of dengue fever. OBSERVATIONS: Young male having history of dengue fever presented with complaints of sudden pain, swelling, redness, and loss of vision in the left eye. His clinical features and radiographic examination were suggestive of orbital cellulitis with pan-ophthalmitis, which rapidly progressed to endophthalmitis. CONCLUSION: This case highlights the role of orbital vessels as a possible route for occurrence of endophthalmitis in a case of orbital cellulitis.

Human Guanylate-Binding Protein 1 Positively Regulates Japanese Encephalitis Virus Replication in an Interferon Gamma Primed Environment.

RNA virus infection triggers interferon (IFN) receptor signaling, leading to the activation of hundreds of interferon-stimulated genes (ISGs). Guanylate-binding proteins (GBPs) belong to one such IFN inducible subfamily of guanosine triphosphatases (GTPases) that have been reported to exert broad anti-microbial activity and regulate host defenses against several intracellular pathogens. Here, we investigated the role of human GBP1 (hGBP1) in Japanese encephalitis virus (JEV) infection of HeLa cells in both an IFNγ unprimed and primed environment. We observed enhanced expression of GBP1 both at transcript and protein levels upon JEV infection, and GBP1 association with the virus replication membranes. Depletion of hGBP1 through siRNA had no effect on JEV replication or virus induced cell death in the IFNγ unprimed environment. IFNγ stimulation provided robust protection against JEV infection. Knockdown of GBP1 in the primed environment upregulated expression and phosphorylation of signal transducer and activator of transcription 1 (STAT1) and significantly reduced JEV replication. Depletion of GBP1 in an IFNγ primed environment also inhibited virus replication in human neuroblastoma SH-SH5Y cells. Our data suggests that in the presence of IFNγ, GBP1 displays a proviral role by inhibiting innate immune responses to JEV infection.